U.S. patent number 5,750,066 [Application Number 08/445,268] was granted by the patent office on 1998-05-12 for method for forming an intermittent stream of particles for application to a fibrous web.
This patent grant is currently assigned to The Procter & Gamble Company. Invention is credited to James Michael Fleming, Michael Francis Vonderhaar.
United States Patent |
5,750,066 |
Vonderhaar , et al. |
May 12, 1998 |
Method for forming an intermittent stream of particles for
application to a fibrous web
Abstract
The present invention provides a method and apparatus for
applying discrete particles of absorbent material to a
predetermined location on a fibrous web. The apparatus comprises a
continuously rotating mask, and a means for directing a supply
stream of absorbent particles to form an acute included angle with
a diverting surface on the rotating mask. The mask diverting
surface splits the supply stream of absorbent particles into a
first intermittent stream passing through the mask and a second
intermittent stream deflected by the diverting surface. The
absorbent particles in one of the first and second intermittent
streams is directed to the fibrous web.
Inventors: |
Vonderhaar; Michael Francis
(Cincinnati, OH), Fleming; James Michael (Cincinnati,
OH) |
Assignee: |
The Procter & Gamble
Company (Cincinnati, OH)
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Family
ID: |
22485765 |
Appl.
No.: |
08/445,268 |
Filed: |
May 19, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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139249 |
Oct 19, 1993 |
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Current U.S.
Class: |
264/510; 264/517;
264/518 |
Current CPC
Class: |
A61F
13/15658 (20130101) |
Current International
Class: |
A61F
13/15 (20060101); B27N 003/02 () |
Field of
Search: |
;264/517,518,257,510
;425/80.1,81.1,83.1 ;156/62.2,62.4 ;118/301,304 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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29 42 163 A1 |
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Apr 1981 |
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DE |
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2 150 033 |
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Jun 1985 |
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GB |
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WO9324290 |
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Dec 1993 |
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WO |
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Primary Examiner: Kuhns; Allan R.
Attorney, Agent or Firm: Gressel; Gerry S. Huston; Larry L.
Linman; E. Kelly
Parent Case Text
This is a divisional of application Ser. No. 08/139,249, filed on
Oct. 19, 1993, now abandoned.
Claims
What is claimed is:
1. A method for forming an intermittent stream of discrete
particles for application to a fibrous web, the method comprising
the steps of:
forming a supply stream of the discrete particles, wherein at least
some of the discrete particles comprise an absorbent gelling
material;
continuously moving a mask having a diverting surface relative to
the stream of discrete particles; and
directing the supply stream of discrete particles to form an acute
included angle with the diverting surface and splitting the supply
stream of discrete particles into a first intermittent stream
passing through the mask and a second intermittent stream deflected
by the diverting surface.
2. The method of claim 1 comprising the step of directing discrete
particles in one of the intermittent streams to apply a nonuniform
distribution of discrete particles to the fibrous web.
3. A method for applying discrete particles to a fibrous web, the
method comprising the steps of:
supporting the fibrous web;
conveying the fibrous web;
providing a supply stream of discrete particles, wherein at least
some of the discrete particles comprise an absorbent gelling
material;
supporting a mask having a diverting surface for continuous
rotation about an axis;
continuously rotating the mask about the axis;
directing the supply stream of discrete particles to form an acute
included angle with the diverting surface and splitting the supply
stream of discrete particles into a first intermittent stream of
particles passing through the mask and a second intermittent stream
of particles deflected by the diverting surface; and
directing the discrete particles in one of the intermittent streams
to the fibrous web.
4. A method for forming airlaid fibrous webs having discrete
particles, the method comprising the steps of:
providing an airlaying means having a foraminous forming element
for forming an airlaid fibrous web;
providing an air-entrained stream of fibers;
providing an air-entrained supply stream of discrete particles;
supporting a mask for continuous rotation of a diverting surface
about an axis;
continuously rotating the mask about the axis;
directing the supply stream of discrete particles to form an acute
included angle with the diverting surface for splitting the supply
stream of discrete particles into a first intermittent stream of
particles passing through the mask and a second intermittent stream
of particles deflected by the diverting surface;
combining the air-entrained stream of fibers with one of the
intermittent streams of particles to form a combined stream
comprising an intermittent stream of particles within a continuous
stream of fibers; and directing the combined stream of fibers and
particles to the forming element of the airlaying means.
5. The method of claims 3 or 4 wherein the supply stream of
discrete particles is directed to form an included angle of less
than 60 degrees with the diverting surface.
6. The method of claim 5 wherein the supply stream of discrete
particles is directed to form an included angle of about 20 to
about 30 degrees with the diverting surface.
7. The method of claims 3 or 4 further comprising the step of
phasing the position of the mask with the position of the web.
8. The method of claims 3 or 4 including the step of inclining the
diverting surface with respect to the horizontal axis.
9. The method of claim 8 wherein the step of directing the supply
stream of discrete particles to form an acute included angle with
the diverting surface comprises directing the supply stream of
discrete particles with a vertically downward velocity
component.
10. The method of claim 4 comprising the step of combining the
air-entrained supply stream of fibers with the first intermittent
stream of particles passing through the mask.
11. The method of claim 4 wherein the step of providing an
air-entrained supply stream of discrete particles comprises:
providing a metered quantity of discrete particles;
combining the metered quantity of discrete particles with the
second intermittent stream of discrete particles deflected by the
mask; and
entraining the combined metered and deflected particles in an
airflow to form an air-entrained supply stream of discrete
particles.
12. The method of claim 4 wherein the step of providing an
air-entrained supply stream of discrete particles comprises
providing an air-entrained supply stream of discrete particles
wherein at least some of the discrete particles comprise an
absorbent gelling material.
13. The method of claim 3 comprising the step of directing discrete
particles in one of the intermittent streams to apply a nonuniform
distribution of discrete particles to the fibrous web.
14. The method of claim 4 comprising the step of directing discrete
particles in one of the intermittent streams to apply a nonuniform
distribution of discrete particles to the fibrous web.
Description
FIELD OF THE INVENTION
This invention is related to a method and apparatus for forming
fibrous webs having a predetermined distribution of particulate
material. More particularly, the invention is related to forming an
intermittent stream of particulate material for application to a
fibrous web.
BACKGROUND OF THE INVENTION
Absorbent articles such as disposable diapers, incontinence pads,
and catamenial napkins generally include an absorbent core for
receiving and holding body exudates. The absorbent core typically
includes a fibrous web, which can be a nonwoven, airlaid web of
natural or synthetic fibers. A class of particulate absorbent
materials known as superabsorbent polymers or absorbent gelling
materials can be incorporated in the fibrous web to improve the
absorption and retention characteristics of the fibrous web.
Because absorbent gelling materials are generally significantly
more expensive than readily available natural or synthetic fiber
materials (e.g., cellulose fibers), it is advantageous to reduce
the quantity of absorbent gelling material in the core. Rather than
uniformly reducing such particles throughout the entire core, it is
desirable to distribute the particles in the absorbent core in a
predetermined manner so that the particles are located where they
will be most effective in acquiring and retaining body
exudates.
Various techniques have been developed to distribute and locate
absorbent materials on or within a fibrous substrate. U.S. Pat. No.
4,800,102 issued to Takada discloses applying a powder to the top
surface of a substrate by spraying powder through an opening in a
rotating disc member. Powder not passing through the opening is
shown to be supported on a horizontal surface of the disc as the
disc rotates, and is subsequently scraped from the disc by a
scraper into a receiving member below the scraper. Powder not
removed by the scraper is removed by a vacuum sucker positioned
above the disc. Such an arrangement is disadvantageous because it
requires powder material to accumulate on the disc. The arrangement
requires a relatively complicated scraper and vacuum device to
remove powder from the disc. Centrifugal forces may cause some of
the accumulated powder to be flung from the disc, thereby
complicating powder recycling. Powder accumulating on the disc
prior to removal may also cause rotary imbalance and vibration of
the disc, especially if the disc is rotated at the relatively high
speeds desirable for cost effective production rates. Further, the
powder material is shown to be directed generally perpendicular to
the disc surface. Therefore, powder material may strike and bounce
off of the disc in an unpredictable direction, thereby further
complicating powder recycling.
U.S. Pat. No. 5,028,224 issued to Pieper et al. discloses pulsing
and diverting mechanisms for producing an intermittent flow of
absorbent particles. The diverting mechanism includes a flap which
rotates about a pivot between a closed position and an open
position to provide an intermittent quantity of particulate
material. Such an arrangement is undesirable because operation of
such a flap between the open and closed positions requires
accelerating and decelerating the flap between two stationary
positions. Operating such a reversing mechanism at high speeds can
result in undesirable inertial forces in the mechanism, and
complicates precise control of the definition of the pulse of the
particulate material.
U.S. Pat. No. 5,213,817 issued to Pelley discloses a stream of
powder material passing through a nozzle which is movable between
first and second positions. A flow separator splits the stream into
two intermittent streams as the nozzle is moved between the first
and second positions. As in Pieper et al. above, such an
arrangement is undesirable because operation of the nozzle between
two positions requires accelerating and decelerating the nozzle
between two stationary positions. Reversing the direction of motion
of the nozzle at high speeds results in undesirable inertial
forces, and complicates precise control of the definition of the
pulse of particulate material.
Accordingly, it is an object of the present invention to provide an
apparatus and method for applying discrete particles to a fibrous
web. It is another object of the present invention to provide a
pulse of discrete particles for application to a predetermined
location on a fibrous web. Another object of the present invention
is to provide a continuously rotating mask having a particle
diverting surface forming an acute included angle with a supply
stream of particles to split the stream of discrete particles into
a first intermittent stream passing through the mask and a second
intermittent stream deflected by the diverting surface.
SUMMARY OF THE INVENTION
The present invention comprises an apparatus for and method of
applying discrete particles to a predetermined location on a
fibrous web. The apparatus includes a conveyor for supporting and
moving the fibrous web; a means for forming a supply stream of
discrete particles; a mask moving continuously relative to the
supply stream of particles; a diverting surface on the mask for
splitting the supply stream of particles into a first intermittent
stream passing through the mask and a second intermittent stream
deflected by the diverting surface; a means for directing the
supply stream of discrete particles to form an acute included angle
with mask diverting surface; and a means for directing the discrete
particles in one of the intermittent streams of particles to the
fibrous web.
The apparatus can include a foraminous forming element for forming
an airlaid fibrous web; means for forming an air-entrained flow of
fibers; means for combining the flow of fibers with one of the
first and second intermittent streams to form a combined stream
comprising an intermittent stream of particles within a continuous
stream of fibers; and means for directing the combined stream of
fibers and particles to the forming element. In a preferred
embodiment, the mask is supported for continuous rotation about an
axis, and the supply stream of discrete particles forms an included
angle of less than 45 degrees with the diverting surface.
The method preferably comprises the steps of:
a. providing an airlaying means having a foraminous forming element
for forming a fibrous web;
b. providing an air-entrained stream of fibers;
c. providing an air-entrained supply stream of discrete
particles;
d. providing a mask having a diverting surface;
e. continuously rotating the mask about an axis;
f. directing the supply stream of discrete particles to form an
acute included angle with the diverting surface for splitting the
stream of discrete particles into a first intermittent stream of
particles passing through the mask and a second intermittent stream
of particles deflected by the diverting surface;
g. combining the stream of fibers with one of the intermittent
streams of particles to form a combined stream comprising an
intermittent stream of particles within a continuous stream of
fibers; and
h. directing the combined stream of fibers and particles to the
forming element of the airlaying means.
BRIEF DESCRIPTION OF THE DRAWINGS
While the specification concludes with claims particularly pointing
out and distinctly claiming the present invention, it is believed
the present invention will be better understood from the following
description in conjunction with the accompanying drawings in
which:
FIG. 1 is a perspective view of an absorbent article shown
partially cut-away.
FIG. 2 is a cross-sectional view of an absorbent core having a
dusting layer and a layer including discrete particles of absorbent
material.
FIG. 3 is a schematic illustration of an apparatus according to one
embodiment of the present invention having one particle recycling
arrangement.
FIG. 4 is a schematic illustration of an apparatus according to an
alternate embodiment of the present invention having an alternative
particle recycling arrangement.
FIG. 5 is a cross-sectional side view of the mask supported in an
enclosure and the mask delivery nozzle.
FIG. 6 is a view taken along line 6--6 in FIG. 5 showing the mask
supported in the enclosure, with the enclosure partially
cut-away.
FIG. 7 is a plan view of a mask having apertures in the diverting
surface.
FIG. 8 is a schematic illustration of a longitudinal distribution
of particulate material in an absorbent core.
FIG. 9 is a plan view of a mask having apertures with different
radial widths for forming a lateral distribution of particles shown
in FIG. 11.
FIG. 10 is a schematic illustration of a means for providing
phasing of the position of the mask with the position of the
foraminous forming element.
FIG. 11 is a schematic illustration of a lateral distribution of
particulate material in an absorbent core.
DETAILED DESCRIPTION OF THE INVENTION
While the present invention will be described in the context of
providing airlaid fibrous webs for use as absorbent cores in
disposable absorbent articles such as disposable diapers, the
present invention may also be employed to provide absorbent webs
for use in a number of other articles, including but not limited to
incontinence briefs, disposable training pants, and sanitary
napkins.
FIG. 1 shows a disposable diaper 20 having a liquid pervious
topsheet 22, a liquid impervious backsheet 24, and an absorbent
core 26 disposed between the topsheet 22 and the backsheet 24.
Preferred constructions of such disposable diapers are described in
U.S. Pat. No. 3,860,003 issued Jan. 14, 1975 to Buell and U.S. Pat.
No. 5,151,092 issued Sep. 29, 1992 to Buell et al., which patents
are incorporated herein by reference. The diaper 20 has a
longitudinal centerline 21 and a lateral centerline 23. As used
herein, the "longitudinal" dimension, direction, or axis of the
diaper 20 is aligned front to back with respect to the wearer as
the disposable absorbent article is worn. The "lateral" dimension,
direction, or axis of the diaper 20 is perpendicular to the
longitudinal direction and is sideways aligned as the diaper is
worn.
The absorbent core 26 can include two or more components, such as a
first insert core component 32 and a second shaped core component
34. Preferred absorbent core constructions are described in U.S.
Pat. No. 4,673,402 issued Jun. 16, 1987 to Weisman et al.; U.S.
Pat. No. 4,685,915 issued Aug. 11, 1987 to Hasse et al.; U.S. Pat.
No. 4,834,735 issued May 30, 1989 to Alemany et al.; U.S. Pat. No.
5,217,445 issued Jun. 8, 1993 to Cook et al.; and U.S. Pat. No.
5,234,423 issued Aug. 10, 1993 to Alemany et al., which patents are
incorporated herein by reference. The insert core component 32
serves to collect and distribute discharged body fluid, and can
comprise a web of hydrophilic fiber material. The insert core
component 32 can be free of particles of absorbent gelling
material, or alternatively, can include an amount of particles of
such material.
The shaped core component 34 absorbs discharged body fluids from
the insert core component 32 and retains such fluids. As shown in
FIGS. 1 and 2, the shaped core component 34 includes a thin dusting
layer 35 of hydrophilic fiber material overlayed by a primary layer
36 of a combination of hydrophilic fiber material and discrete
particles 38 of substantially water insoluble, fluid absorbing,
absorbent gelling materials. While the dusting layer 35 is
preferably a relatively thin layer of hydrophilic fiber material,
it should be understood that the term "dusting layer" denotes a
layer of the fibrous web and includes layers having any
thickness.
There are several suitable absorbent gelling materials which can be
used to form the discrete particles 38 in the shaped core component
34, such as silica gels or organic compounds such as crosslinked
polymers. Particularly preferred absorbent gelling materials are
hydrolyzed acrylonitrile grafted starch, acrylic acid grafted
starch, polyacrylates and isobutylene maleic anhydride copolymers,
or mixtures thereof. U.S. Pat. Re 32,649 reissued to Brandt et al.
Apr. 19, 1988 is incorporated herein by reference for the purpose
of showing suitable absorbent gelling materials.
FIG. 3 shows an apparatus according to the present invention for
forming an intermittent stream of absorbent gelling material
particles and applying the intermittent stream of materials to a
fibrous web. An intermittent stream of particles is a stream of
particles having a particle flow rate which is periodically stopped
or reduced. The apparatus includes a conveyor for supporting and
moving a fibrous web, and preferably comprises an airlaying means
such as a rotating drum-type airlaying module 40 having a
foraminous forming element, such as a foraminous forming drum 42.
Airlaying module 40 is suitable for forming an airlaid fibrous web
41, such as shaped core component 34.
The apparatus also preferably includes a means for forming an
air-entrained stream of fibers 62, such as a disintegrator 70. The
apparatus further includes a means for forming a supply stream 82
of discrete absorbent gelling material particles 38 such as a
particle metering device 80 and an eductor 90.
The apparatus according to the present invention includes a mask
100 continuously moving with respect to the supply stream 82 of
discrete particles. In a preferred embodiment the mask 100 is
continuously rotated about an axis 101. The mask can be rotated
about axis 101 by any suitable means, such as by a motor 104 and
shaft 102 shown in FIG. 3. The mask 100 includes a diverting
surface 110 for splitting the supply stream 82 of discrete
particles into a first intermittent stream 103 of particles passing
through the mask 100 and a second intermittent stream 105 of
particles deflected by the diverting surface 110.
The apparatus according to the present invention also includes a
means for directing the supply stream 82 of discrete particles to
form an acute included angle A (FIG. 5) with the diverting surface
110. The means for directing the supply stream 82 to form an acute
included angle A with the diverting surface 110 can include a mask
delivery nozzle 120, shown in FIGS. 3, 4, 5, and 6. The apparatus
can further include a means for combining the stream of fibers 62
with the first intermittent stream 103, such as a diverging duct
65, to form a combined stream 66 comprising an intermittent stream
of particles within a continuous stream of fibers. A means for
directing the combined stream 66, such as a drum hood 50, directs
the combined stream 66 to the foraminous forming element 42 of the
airlaying apparatus 40.
Referring to the components in FIG. 3 in more detail, the
disintegrator 70 can include a rotary element 74 enclosed in a
housing 72. The disintegrator 70 receives a fibrous sheet material
71 capable of being separated into individual fibers. The fibrous
sheet material 71 can include synthetic and/or natural fibers, and
preferably comprises cellulosic fibers. The rotary element 74 can
be continuously driven in the direction shown in FIG. 3. Teeth on
the rotary element 74 separate the individual fibers of the sheet
material 71 as the sheet material 71 is fed into the disintegrator
70.
The disintegrator 70 can include splitter chute 76 for forming
multiple streams of air-entrained fibers from the individual fibers
separated by the rotary element 74. The splitter chute 76 can be
directly or indirectly joined to or disposed within the housing 70.
The splitter chute 76 provides the air-entrained stream of fibers
62, as well as a dusting layer air-entrained steam of fibers 63 for
forming the dusting layer 35 shown in FIG. 2. The air-entrained
stream of fibers 62 is carried from the splitter chute 76 by
conduit 60, and the dusting layer air-entrained stream of fibers 63
is carried from the splitter chute 76 by dusting layer conduit
67.
U.S. Pat. Nos. 4,908,175 and 4,765,780, issued Mar. 13, 1990 and
Aug. 23, 1988, respectively, to Angstadt et al., are incorporated
herein by reference for the purpose of showing the construction of
a suitable disintegrator 70 and splitter chute 76 for providing the
air-entrained stream of fibers 62 and the dusting layer
air-entrained stream of fibers 63. However, it will be understood
by those skilled in the art that other apparatus for separating a
roll or mat of fibrous material into individual fibers, including
but not limited to hammermills, fiberizers, picker rolls, and
lickerin rolls, may be used to provide the air-entrained streams of
fibers 62 and 63.
The airlaying module 40 includes the rotating foraminous forming
drum 42 on which the fibrous webs 41 can be formed. The foraminous
forming drum 42 can include a plurality of formation cavities 44
circumferentially spaced about the periphery of the forming drum
42. Five formation cavities 44 are shown in FIG. 3, with each
formation cavity 44 having a circumferential span of about
seventy-two degrees. The forming drum 42 is rotated by a motor 45
(FIG. 10) or other suitable device. The forming drum 42 rotates in
the direction shown in FIG. 3 such that fibers in the dusting layer
air-entrained stream of fibers 63 are first deposited in the
formation cavities 44 to form the dusting layer 35 shown in FIG. 2.
The combined stream 66 is then deposited in cavities 44 to overlay
the dusting layer and form the primary layer 36 comprising a
combination of hydrophilic fiber material and discrete particles of
absorbent gelling materials.
The airlaying module 40 includes a plurality of vacuum chambers
(not shown) within the interior of the foraminous forming drum 42.
Each of the vacuum chambers is connected to a suitable source of
vacuum (not shown). Entrainment air for forming air-entrained
streams of fibers 62 and 63 is drawn through the foraminous forming
drum 42 by the vacuum maintained in the vacuum chambers within the
interior of the forming drum 42. U.S. Pat. No. 4,592,708 issued
Jun. 3, 1986 to Feist et al. and above referenced U.S. Pat. Nos.
4,908,175 and 4,765,780 are incorporated herein by reference for
the purpose of showing a suitable airlaying module 40 for use with
the present invention.
FIG. 3 shows one embodiment of the present invention. Discrete
particles 38 of absorbent gelling material are directed from a
supply source (not shown) to branched conduit 307 as indicated by
arrow 305. A valve associated with branched conduit 307 is movable
from a first position 309A to a second position 309B shown in
phantom.
In a first operating mode the valve is positioned in the first
position 309A so that the discrete particles 38 of absorbent
gelling material are directed to and accumulated in a filter
receiver vessel 300. Air in filter receiver vessel 300 is removed
through a filter 330 and air conduit 320 by a suitable vacuum
source 340.
The particles in filter receiver vessel 300 are gravity fed to the
particle metering device 80. The metering device 80 delivers a
predetermined mass of discrete particles 38 per unit time. The
metering device 80 can include a hopper 84, screw feeder 86, and
scale 88. A suitable metering device is an Acrison Volumetric
Feeder, Model No. 405-105X-F, available from Acrison, Inc. of
Moonachie, N.J.
The metered quantity of particles 38 is delivered by screw feeder
86 to a funnel receiver 91 and directed to an eductor 90. Eductor
90 entrains the metered quantity of particles 38 within a motive
air flow to provide the air-entrained supply stream 82 of discrete
particles. The motive air flow can be provided by a suitable blower
92. A suitable eductor 90 is a Fox Eductor, Model No. 612046,
available from the Fox Valve Development Corporation, of Dover,
N.J. A suitable blower 92 is a Fuji Blower, Model VFC503A,
available from the Fuji Electric Corporation of America, Lincoln
Park, N.J.
The air-entrained supply stream 82 of discrete particles is carried
by a particle carrying conduit, which can comprise a particle
delivery chute 94 and the delivery nozzle 120. The delivery chute
94 carries the supply stream 82 of discrete particles to the mask
delivery nozzle 120. The mask delivery nozzle 120 directs the
supply stream 82 to form an acute included angle A with the
diverting surface 110 of the mask 100. The particles 38 in the
first intermittent stream 103 passing through the mask 100 are
combined with the air-entrained stream of fibers 62 in the
diverging duct 65, and directed to the foraminous forming drum 42
by the hood 50.
The particles 38 in the second intermittent stream 105 are
deflected by the diverting surface 110 of the mask 100. The
momentum of the particles in the second intermittent stream 105
carries the particles in a predetermined direction (vertically
downward in FIG. 3) to enter a conduit 410. The deflected particles
are carried in the conduit 410 for recycling. In the embodiment
shown in FIG. 3, the conduit 410 carries the diverted particles to
vacuum receiving chamber 400. A vacuum source 450 provides an
airflow through a particle filter 430 for drawing the particles in
conduit 410 into the vacuum receiving chamber 400. A suitable
vacuum source 450 is commercially available from the Buffalo Forge
Company of Buffalo, N.Y. as Model No. 3RE.
The recycled particles accumulate in the vacuum receiving chamber
400 during the first operating mode. In a second operating mode,
the valve associated with branched conduit 307 is moved to position
309B, thereby blocking the flow 305 of discrete particles from the
supply source. With the valve in position 309B, a rotary air lock
420 positioned under the vacuum receiving chamber 400 is rotated to
gravity feed at least a portion of the accumulated recycled
particles in chamber 400 into a pick-up pan 490. The rotary air
lock 420 permits the accumulated recycled particles in chamber 400
to enter the pick-up pan 490, while maintaining the vacuum in
chamber 400 provided by the vacuum source 450. A suitable rotary
air lock 420 is available from Prater Industries, Inc. of Chicago,
Ill. as Model No. PAV-6C. A blower 492 is activated to provide a
motive air flow for carrying the recycled particles entering
pick-up pan 490 through a conduit 493. The recycled particles
carried in conduit 493 pass through branched conduit 307 and into
the filter receiver vessel 300.
The apparatus is returned to the first operating mode by
deactivating the rotary air-lock 420 and the blower 492, and by
moving the valve associated with the branched conduit 307 to
position 309A. The transition between the first and second
operating modes can be made at a predetermined time-interval, or
alternatively, can be made based on the amount of recycled
particles accumulated in the chamber 400.
FIG. 4 shows an alternative embodiment of the present invention for
providing an air-entrained stream 82 of discrete particles and
recycling the second intermittent stream 105 of particles not
combined with the air-entrained stream of fibers 62. Discrete
particles 38 of absorbent gelling material are carried by a conduit
310 from a supply source (not shown) to a filter receiver vessel
300 as indicated by arrow 305. A vacuum source 340 provides a
motive air flow through a particle filter 330 and a conduit 320 for
carrying the discrete particles into the vessel 300.
The particles in filter receiver vessel 300 are gravity fed to the
particle metering device 80. The metering device 80 delivers a
predetermined mass of discrete particles per unit time. The
metering device 80 can include a hopper 84, screw feeder 86, and
scale 88 as described above with reference to FIG. 3. The metered
quantity of particles is delivered by screw feeder 86 to a finnel
receiver 91 and carried by a conduit 93. The conduit 93 empties the
metered quantity of discrete particles into the conduit 410, so
that the metered quantity of discrete particles is combined with
the second intermittent stream 105 of particles deflected by the
mask 100. Both the conduit 93 and the conduit 410 can be inclined
vertically downward to provide gravity assisted feeding of the
metered quantity of particles and the detected particles. The
combined stream of metered and defected particles is indicated by
arrow 412 in FIG. 4.
The conduit 410 directs the combined stream of particles 412 to an
eductor 90. The eductor 90 and a blower 92 entrain the combined
stream of particles 412 within a motive air flow to provide the
air-entrained supply stream 82 of discrete particles. A suitable
eductor 90 is a Fox Eductor, Model No. 300-SCE-SS available from
the Fox Valve Development Corporation. A suitable blower 92 is a
Cooper/Sutorbilt Blower, Model 3M Legend, also available from the
Fox Valve Development Corporation. The air-entrained supply stream
82 of discrete particles is carried by a conduit 97 to a particle
carrying conduit comprising the particle delivery chute 94 and the
mask delivery nozzle 120. The chute 94 directs the supply stream 82
of particles to the mask delivery nozzle 120.
The conduit 97 can have a circular cross-section with an inner
diameter of about 6.0 cm (2.4 in.) and can include bends 98 and 99
having a radius at the center of the duct cross-section of at least
about 30 cm (12 in.). The bends 98, 99 and the particle delivery
chute 94 preferably lie in a common plane, which common plane is
parallel to the plane of FIG. 4 and passes through the center of
the forming cavities 44. The bends 98, 99 help to center the
particles in the conduit 97 in this common plane. Positioning the
bends 98, 99 and the chute 94 in this common plane aids in aligning
the first intermittent stream 103 of particles passing through the
mask 100 within the forming cavities 44.
The embodiment shown in FIG. 4 provides a metered quantity of
discrete particles, combines the metered quantity of discrete
particles with the second intermittent stream 105 of discrete
particles deflected by the mask, entrains the combined metered and
deflected discrete particles in an air flow to form an
air-entrained supply stream 82, and directs the air-entrained
supply stream 82 of discrete particles to form an acute included
angle A with the mask 100.
The embodiment shown in FIG. 4 is advantageous in that it does not
require the two mode operation of FIG. 3. The embodiment shown in
FIG. 4 is also advantageous because the discrete particles
deflected by the mask 100 for recycling are continuously mixed with
freshly metered discrete particles from the metering device 80.
Such an arrangement provides recycling of the discrete particles
which is independent from the supply source (not shown) of the
discrete particles. Therefore, the embodiment shown in FIG. 4 can
be easily adapted to different production sites having different
types or arrangements of supply sources of the discrete
particles.
In one embodiment of the present invention, the air-entrained
stream of fibers 62 can comprise about 1 to about 24 kg/minute of
fiber carried in an air stream having a velocity of about 610
meter/minute (2,000 feet/minute) to about 4,600 meter/minute
(15,000 feet/minute) and an air flow rate of about 3.8 cubic
meters/minute (136 cubic feet/minute) to about 29 cubic
meters/minute (1,020 cubic feet/minute). The air-entrained stream
of particles 82 can comprise about 1 kg/minute to about 20
kg/minute of particles carried in an airstream having a velocity of
about 610 meter/minute (2,000 feet/minute) to about 3,700
meter/minute (12,000 feet/minute) and an air flow rate of about 1.7
cubic meters/minute (60 cubic feet/minute) to about 10.2 cubic
meters/minute (360 cubic feet/minute).
FIG. 5 is a cross-sectional side view of the mask 100 and the mask
delivery nozzle 120. The mask 100 is shown disposed within an
enclosure 140. FIG. 6 is a front elevation view of the enclosure
140 taken along line 6--6 in FIG. 5, with the enclosure 140
partially cut-away. FIGS. 7 and 9 show different embodiments of the
mask 100.
Referring back to FIG. 5, the mask delivery nozzle 120 can be an
extension of the particle delivery chute 94. The mask delivery
nozzle 120 directs the air-entrained supply stream 82 of discrete
particles to form an acute included angle A with the diverting
surface 110. The term "acute angle" refers to an angle less than
ninety (90) degrees. The angle A is measured from the imaginary
axis 83 along which the air-entrained stream of discrete particles
82 is directed, rather than from the surface of the supply stream
82, which may diverge or converge slightly with respect to the axis
83 of the stream 82. If the axis 83 is curved, the angle A is
measured from the tangent of the axis 83 where the axis 83
intersects the plane of the diverting surface 110.
Referring to FIGS. 5 and 6, the mask 100 is preferably supported
for rotation in a cavity 143 within an enclosure 140. The enclosure
140 isolates the mask 100 and the particle streams 82, 103, and 105
from surrounding conditions which might otherwise adversely affect
the formation of the particle stream 103. In particular, the cavity
143 in the enclosure 140 is closed to surrounding atmospheric
conditions to maintain the air flows which carry particle streams
82, 103, and 105. The enclosure 140 also serves as a containment
structure for holding particle dust.
The enclosure 140 includes an upstream wall 150, a downstream wall
160, a top wall 155, and side walls 157, 159. A trough 408 can be
joined to the bottom of the enclosure 140 for receiving particles
deflected by the diverting surface 110. The trough 408 can include
one or more vents 409 for providing an air passage into the trough
408 and the conduit 410. Such an air passage provides air for
carrying particles in the conduit 410.
The upstream and downstream wall 150 and 160 are parallel to and
closely spaced from the mask 100. The spacing between the upstream
wall 150 and the mask 100 is preferably about 1.1 cm (0.43 inch).
The spacing between the downstream wall 160 and the mask 100 is
preferably no more than about 0.3 cm (0.12 inch). The spacing
between the upstream wall 150 and the mask 100 is greater than the
spacing between the downstream wall 160 and the mask 100 in order
to provide a flow path for the deflected intermittent stream 105 of
discrete particles.
The mask delivery nozzle 120 extends through an aperture 152 in the
upstream wall 150. The delivery nozzle 120 can have an elongated
internal passage 124 oriented radially from the axis 101 of the
mark 100. The elongated passage 124 can have a height D of about
1.7 cm (0.69 inch) and a width W (FIG. 6) of about 9.4 cm (3.7
inch). The delivery nozzle 120 has a beveled face 122 parallel to
the mask 100 and positioned intermediate the upstream wall 150 and
the mask 100 to provide close spacing of the nozzle 120 from the
diverting surface 110. The beveled face 122 is preferably spaced a
distance 123 from the mask 100 of about 0.8 cm (0.3 inch) to
precisely direct the air-entrained supply stream 82 of discrete
particle against the diverting surface 110.
The downstream wall 160 includes a downstream passageway 162 for
receiving the first intermittent stream 103 of particles passing
through the mask. The passageway 162 can converge in the downstream
direction from an upstream entrance enlarged with respect to the
internal passageway 124, as shown in FIG. 5. The enlarged upstream
entrance of the passageway 162 aids in capturing all particles
passing through the mask 100.
An adapter 170 joins the downstream wall 160 to the diverging duct
65. A passageway 172 extending through the adapter 170 provides a
flowpath through which the first intermittent stream 103 of
discrete particles enters the diverging duct 65. In a preferred
embodiment the axis 119 of the first intermittent stream 103 of
particles forms an angle G of about 10 degrees to about 50 degrees
with the air-entrained stream of fibers 62, and most preferably
about 24 degrees.
FIG. 8 shows a longitudinal distribution of absorbent gelling
material particles in an absorbent core, as measured along the
longitudinal axis 21 of the diaper 20 shown in FIG. 1. The
distribution includes a relatively high basis weight region 1003, a
relatively low basis weight region 1002, and transition regions T
between the high and low basis weight regions 1002 and 1003. As the
mask 100 rotates about axis 101, the air-entrained supply stream 82
of particles is intermittently interrupted by the diverting surface
110 and split into the first and second intermittent streams 103
and 105.
In one embodiment the mask 100 can rotate once for each fibrous web
41 formed on drum 42, in which case, the distribution shown in FIG.
8 corresponds to the distribution of absorbent particles along the
length of one shaped core component 34. In other embodiments it may
be desirable to rotate the mask 100 more or less than one
revolution for each fibrous web 41 formed on drum 42.
As shown in FIG. 7, the diverting surface 110 can comprise a
circular sector, such as a sector of a disk. The diverting surface
110 can subtend an angle B from a leading edge 111 to a trailing
edge 113. The relatively high basis weight region 1003 corresponds
to those angular positions of the mask 100 where relatively little,
or none, of the supply stream 82 of discrete particles is deflected
by the diverting surface 110. The relatively low basis weight
region 1002 corresponds to those angular positions of the mask 100
where a relatively large percentage, or all, of the stream of
particles 82 is deflected by the diverting surface 110. The
transition regions T correspond to those angular positions of the
mask 100 where the leading and trailing edges 111 and 113 intersect
the supply stream 82 of particles.
The mask 100 is supported for continuous motion with respect to the
air-entrained stream of particles 82 to avoid the inertial forces
and design and control complexities associated with an apparatus
that accelerates and decelerates between two stationary positions.
In a preferred embodiment of the present invention, the mask 100 is
supported for continuous rotation about the axis 101. In one
preferred embodiment, the mask 100 is fixed to shaft 102, and shaft
102 is rotatably supported on bearings (not shown). The mask 100 is
preferably rotated at a substantially constant angular velocity to
avoid inertial forces associated with angular acceleration and
deceleration. By a "substantially constant angular velocity" it is
meant that the mask 100 is rotated to maintain an angular velocity
of within about 2 percent of a baseline angular velocity, with it
being understood that the rotational speed of the mask 100 may be
temporarily increased or decreased by no more than about 2 percent
of the baseline angular velocity in order to maintain a desired
phasing of the angular position of the mask 100 with the angular
position of the foraminous forming drum 42.
In an alternative embodiment (not shown), the mask 100 can comprise
an endless belt having an apertured surface. The endless belt can
be driven by a motor or other driving means at a generally constant
speed, and the particle nozzle 120 can direct the air-entrained
stream 82 of discrete particles to form an acute included angle A
with the belt surface. The apertured belt surface splits the
air-entrained supply stream 82 of discrete particles into the first
stream 103 passing through the apertures in the belt surface, and
the second stream 105 deflected by the belt surface.
Applicants have found that directing the air-entrained stream of
discrete particles 82 to form an acute included angle A with the
diverting surface 110 provides benefits with respect to pulsing and
recycling the discrete particles. A supply stream 82 of particles
directed normal to the diverting surface 110 could be reflected
backward, into the incoming particle stream 82. Such reflected
particles could disrupt the incoming particle stream, thereby
increasing the transition regions T, or otherwise complicating the
formation of a well defined intermittent stream of particles
passing through the mask 100. Such a well defined intermittent
stream is desirable to provide distinct high and low basis weight
regions 1003 and 1002. In addition, such backward reflected
particles can be scattered in random directions, thereby
complicating recycling of the discrete particles deflected by the
diverting surface 110.
According to the present invention, when the supply stream 82 of
discrete particles is directed to form an acute included angle A
with the diverting surface 110, the deflected particles in the
second intermittent stream 105 will have a component of momentum
parallel to the diverting surface 110. This component of momentum
parallel to the diverting surface will carry the deflected
particles to a predetermined location. Referring to FIG. 5, the
momentum of the deflected particles in the first intermittent
stream 105 carries the deflected particles to a trough 408
connected to the bottom of the enclosure 140. The trough 408 is
joined to the conduit 410 to provide a flow path for recycling of
the deflected particles.
As the angle A is decreased, the component of momentum of the
particles parallel to the diverting surface 110 will increase. The
angle A is preferably less than about sixty degrees, and more
preferably less than about 45 degrees to provide a relatively large
component of particle momentum parallel to the diverting surface
110. However, without being limited by theory, it is believed that
the angle A should be at least about 20 degrees, and can be about
24 degrees to be generally equal to the angle G. Referring to FIGS.
5 and 6, the depth D of the internal passageway 124 has a projected
height H on the diverting surface 110 which is approximately equal
to the depth D divided by the sine of angle A. For a fixed depth D,
the projected height H will increase as the angle A is decreased,
resulting in a longer transition region T in FIG. 8. In one
embodiment of the present invention, the angle A can be between
about 20 to about 30 degrees to provide an adequate component of
particle momentum parallel to the diverting surface 110 without
creating an unacceptably long transition region T.
Referring to FIG. 6, a portion of the downstream wall 160 of the
enclosure 140 is cutaway to show the mask 100 supported for
rotation on the shaft 102. FIG. 6 shows the mask 100 in a position
corresponding to a transition region T, with the trailing edge 113
intersecting the supply stream 82 of discrete particles. It is
generally desirable to decrease the longitudinal length of the
transition region T in order to provide more precise placement of
the absorbent gelling material in the absorbent core. The
longitudinal length of the transition region T decreases with
increasing radial offset S of the internal passageway 124 from the
axis 101 of the mask 100. The transition region T increases with
increasing depth D and with decreasing included angle A. For a mask
rotational speed of about 600 RPM, an angle A between about 20 and
40 degrees, and the width W and depth D listed above, the offset S
can be about 4.8 cm (1.9 inch) to provide an acceptable transition
region T of about 42 degrees of rotation of the mask 100, or about
12 percent of the total longitudinal distribution shown in FIG. 8
corresponding to one rotation of the mask 100.
The nozzle 120 directs the supply stream 82 to have a velocity
component out of the plane of FIG. 6, and a velocity component
directed vertically downward. The mask rotates clockwise in FIG. 6,
as viewed from the downstream side of the mask, and has a
vertically downward velocity component 117 as it intersects the
supply stream 82. It is desirable to rotate the mask 100 such that
the mask 100 intersects the supply stream 82 with a velocity
component 117 parallel to a velocity component of the supply stream
82. Parallel motion of the mask 100 with a velocity component of
the supply stream 82 reduces the chance that the leading edge 111
or the diverting surface 110 will reflect particles backward into
the incoming particle stream 82.
Referring again to FIG. 7, the diverting surface 110 can have one
or more apertures, such as circumferentially extending slots 115.
The slots 115 can be radially spaced apart and radially aligned as
shown in FIG. 7. Two apertures are considered to be radially
aligned if a radial line drawn through the axis 101 intersects both
apertures. The radially spaced apart and radially aligned
circumferentially extending slots 115 shown in FIG. 7 provide a
particle distribution in the low basis weight region 1002 which is
generally uniform in the lateral direction (parallel to the lateral
centerline 23 of the diaper 20), and which has a basis weight
greater than or equal to zero and less than the basis weight in the
relatively high basis weight region 1003.
FIG. 9 shows an embodiment of the mask 100 in which the radial
width of radially spaced apart and radially aligned apertures, such
as the circumferential slots 115A, 115B, and 115C, varies as a
function of radial position of the slots 115. Such a variation in
radial width of the slots 115 can provide a lateral distribution of
particles in the core perpendicular to the longitudinal axis 21.
Such a lateral variation is shown in FIG. 11. For instance, the
variation in radial width shown in FIG. 9 can provide a lateral
particle distribution having a relatively high basis weight region
1013 along the longitudinal centerline 21 of the diaper 20 and
relatively low basis weight regions 1012 laterally outward of the
region 1013. Each slot 115 can have a constant radial width, or
alternatively, one or more of the slots 115 can have a variable
radial width. In an alternative embodiment, circular apertures
having a diameter that varies as a function of radius can be used
to provide a lateral variation in basis weight. Of course, other
aperture shapes can also be used.
In an alternative embodiment (not shown), the diverting surface 110
can comprise an uninterrupted surface having no apertures for
providing a region 1002 having no absorbent gelling material. In
yet another embodiment the diverting surface 110 can extend through
360 degrees and include a circumferentially varying pattern of
apertures for providing two or more regions of different basis
weight in the longitudinal direction. The mask 100 can be formed
from any suitable material which can resist abrasion, including,
but not limited to stainless steel.
In the embodiment shown in FIG. 5, the particle nozzle 120 directs
the air-entrained stream of particles 82 with a vertically downward
velocity component. In addition, the diverting surface 110 may be
inclined with respect to the horizontal plane and may rotate about
an axis 101 inclined with respect to the vertical axis. As shown in
FIG. 5, the axis of rotation 101 of the mask 100 can be horizontal,
and the diverting surface 110 can be vertical. Such an arrangement
has the advantage that gravity assists in directing the deflected
particles in the second intermittent particle stream 105 into the
trough 408 and the conduit 410.
FIG. 10 schematically illustrates a means for maintaining a desired
phasing of the angular position of the mask 100 with the angular
position of the foraminous forming drum 42 in order to maintain the
desired longitudinal distribution of absorbent gelling material in
the absorbent pads formed on the forming drum 42. The means for
maintaining the desired phasing includes a master position resolver
502, a slave position resolver 504, a computer 510, and a motor
controller 530.
The mask 100 is driven directly, or indirectly, by a motor 104
through a drive train which includes the shaft 102. The motor 104
can be a brushless DC electric motor such as is available from the
Reliance Electric Company of Cleveland, Ohio. Forming drum 42 is
driven directly or indirectly by a motor 45 through a drive train
which includes shaft 47. The master position resolver 502 detects
the angular position of shaft 47, or a shaft geared to shaft 47, as
indicated by connection 501. The master resolver 502 provides a
signal representing the position of shaft 47 to the computer 510
via data line 506. The slave position resolver 504 detects the
angular position of the shaft 102, or a shaft geared to the shaft
102, as indicated by connection 526. The slave position resolver
504 provides a signal representing the position of shaft 102 to the
computer 510 via data line 522. Using the input signals from data
lines 506 and 522, the computer 210 determines and sends a
proportionate analog voltage signal to the motor controller 530 via
the data line 528. The motor controller 530 provides a speed signal
to the motor 104 via data line 532 in order to speed or slow the
motor 104 as needed to maintain the angular position of the mask
100 phased with respect to the angular position of the forming drum
42.
In one embodiment, the mask 100 makes one revolution for each
absorbent core, or five rotations for each rotation of a forming
drum 42 having five forming cavities 44. Both the master and the
slave resolvers 502 and 504 are assigned 4096 counts per
revolution. The computer 510 compares the number of counts received
from each of the resolvers in a given time period to determine a
position error of the mask 100 relative to the forming drum 42.
Suitable master and slave position resolvers 502 and 504 are
available from the Reliance Electric Company of Cleveland, Ohio
under the model designation 57C360 or 57C361. A suitable computer
510 is available from the Reliance Electric Company under the name
Reliance AUTOMAX DCS (distributed control system), and includes a
power supply 512, a Reliance Model 7010 CPU 514, a master resolver
card 516, a slave resolver card 518, and an analog output card 520.
A suitable motor controller 530 is a Reliance Model HR2000 motor
controller set to "speed mode." The computer 510 can be configured
and programmed according to the AUTOMAX Programming Reference
Manual, Version 2.0; the AUTOMAX System Operation Manual, Version
3.0; and the AUTOMAX Hardware Reference Manual. In an alternative
embodiment, the mask 100 and the forming drum 42 can be coupled
mechanically to maintain the desired angular phasing, such as with
a timing belt, timing chain, or gear train.
While particular embodiments of the present invention have been
illustrated and described, it would be obvious to those skilled in
the art that various changes and modifications can be made without
departing from the spirit and scope of the invention. For instance,
in the embodiments shown, the particles in one of the intermittent
streams 103, 105 are directed to a web, and the particles in the
other stream are recycled. Alternatively, the particles in both
intermittent streams can be directed for laydown on different webs,
or on different portions of the same web. It is intended to cover,
in the appended claims, all such modifications and intended
uses.
* * * * *